A nothing but：只有
Nothing but a miracle can save her life.
B anything but：
1.单单除...之外
I'll do anything but that. 我什么都做,就是不愿做那件事.
2.根本不
He is anything but clever. 他根本不聪明.
C not to speak of 是指“更不用说,且不提”.
Even riding in a bus makes her sick, not to speak of sailing in a boat. 她连坐公共汽车都晕,更不用说坐船了.
D nothing to speak of 不足挂齿；微不足道...
He said that what he had done was nothing to speak of.
根据意思,觉得这道题目应该选C.意思是：JOHN没钱去上大学,更不用说是去国外了.